The present invention relates to optical devices that use non-linear optical mediums.
In optical waveguides used in optical data transmission and optical laser cavities, light propagates in one spatial direction. These waveguides use total internal reflection at an interface between two media with relatively higher and lower refractive indices to direct the light. Total internal reflection causes the light to propagate in the medium with the higher refractive index.
Periodic dielectric structures can also be used to direct light propagation. In periodic dielectric structures, light propagation is analogous to electron propagation in a crystal. If the wavelength of the light is of the order of the dimensions of the lattice, a photonic bandgap (PBG) forms. The PBG is a wavelength range in which photons cannot propagate through a periodic dielectric structure. If incident light""s wavelength is in the PBG, the incident light is reflected off the periodic dielectric structure rather than transmitted through the structure. Period dielectric structures whose lattice lengths are of the order of wavelengths of near infrared or visible light are often referred to as PBG structures. Light with a wavelength in a PBG can propagate down a narrow channel in a PBG structure.
Proposals exist for using PBG structures to make optical cavities. An article entitled xe2x80x9cTwo-Dimensional Photonic Band-Gap Defect Mode Laserxe2x80x9d by O. Painter et al. appearing in the Jun. 11, 1999 issue of Science (p. 18 et seq.) describes the formation of a laser cavity in a two-dimensional (2D) a 2D PBG structure. The laser cavity is fabricated in a group III-V crystalline semiconductor and uses a channel in a 2D PBG structure and a defect to form the laser cavity.
One aspect of the present invention relates to an integrated optical switch that includes a planar waveguide with a one-dimensional (1D) optical waveguide therein. The 1D waveguide has a specific interaction region that defines a filter. The filter is, at least in part, made of a nonlinear optical medium and is controllable by externally introduced control light. Changing the intensity of the control light causes optical switching by changing the index of refraction of the nonlinear medium so that the filter changes between first and second states. The filter transmits light propagating in the 1D waveguide in the first state and reflects light propagating in the 1D waveguide in the second state.
In some embodiments, the 1D waveguide is formed from a PBG structure and a channel therein. The PBG structure causes the channel to function as a 1D waveguide in which a selected wavelength range of light propagates. The channel is formed of a nonlinear optical medium and includes a resonant cavity formed of a periodic array of holes with a defect. Switching results from applying a control light beam that changes the index of refraction of the medium in the cavity and thus, the resonant frequency of the cavity.
Exemplary switches use PBG structures in III-V semiconductors, e.g., semiconductors comprising elements from the group consisting of gallium (Ga), arsenic (As), indium (In), and phosphorus (P), and wavelengths of control light that generate carrier densities in these semiconductors. The presence of carrier densities strongly modifies the medium""s index of refraction and the resonant frequencies of optical cavities therein. These exemplary switches are able to switch light with wavelengths between about 0.9 and 1.65 xcexcm.
Various embodiments of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.